An igniter for a gas turbine engine should be capable of reliably and cost-effectively igniting a combustible mixture during numerous starts that occur throughout operational cycles of the engine. The igniting function is generally accomplished by electrically-generating a spark across a gap formed between oppositely charged electrodes in a retractable igniter rod. The igniter rod may be a slender columnar structure, which in an ignition-position is deployed into a path of the combustible mixture (e.g., hot gas path) in a combustion chamber. The ignition takes place when velocity and pressure of compressed air in the chamber reach predetermined values.
After ignition, the igniter rod is designed to retract (e.g., to a retracted-position) into a protective structure (e.g., a guide tube) away from the hot combustion environment in response to continued compressor discharge pressure in the chamber throughout a working operational cycle of the engine. A cap is connected to the cold-end of the guide tube, which provides an access passageway for the igniter rod.
The generally slender columnar structure of the igniter rod could make it susceptible to vibration, which commonly develops during normal engine operation, and/or to a load magnification due to cantilever beam loading. In certain situations, this moment loading (e.g., due to gravity on the igniter rod and/or the weight of electrical cables suspended at the cold-end of the rod), could lead to undesirable mechanical-pinching conditions that could affect the movement of the igniter rod within the guide tube near the hot-end of the igniter.